Pop-up greeting cards are three dimensional (3-D) displays that fold flat and open up to display 3-D elements or pop-ups. The cards are generally formed from paper stock or plastic and have two panels connected at a fold line. Pop-up elements are connected to both of the panels and fold as the panels close on each other, allowing the greeting card to basically lie flat. Likewise, as the panels are opened up, the pop-up elements rise to present a 3-D display.
These cards naturally tend to close unless an opening force is maintained. In certain applications, it is desirable to keep the 3-D display opened. A locking mechanism which has been employed in the past is a rectangular piece of cardstock which is adhered to one of the panels at the fold line. This folds outwardly, such that a free edge of the rectangular card stock engages the other of the panels, basically holding the panels at a 90° angle. This mechanism is not particularly effective. The cardstock tends to be flimsy and does not continue functioning over time. It also only holds the card open at 90° or less.